Beta activated ultraviolet radiation source surrounded by a visible light producing fluorescent agent

ABSTRACT

A device having utility as an ultraviolet radiation source comprising a hollow, translucent body formed of an ultraviolet radiation transmitting material. The inner walls of the body define a sealed chamber, and are provided with a thin layer, film, or coating of an ultraviolet radiation emitting phosphor. A low energy beta-electron emitting substance such as tritium is confined within the chamber and is positioned therein to enable the beta-electrons emitted by it to make direct contact with the phosphor. By embedding a fluorescent agent in the material of which the translucent body is formed, or by encapsulating the body in a material containing a fluorescent agent, the device may be utilized to transmit visible light.

United States Patent [191 Isenberg 1 Jan. 22, 1974 BETA ACTIVATEDULTRAVIOLET RADIATION SOURCE SURROUNDED BY A VISIBLE LIGHT PRODUCINGFLUORESCENT AGENT [76] Inventor: Sampson Isenberg, 2400 N.

Lakeview, Chicago, 111. 60612 [22] Filed: Dec. 30, 1970 [21] Appl. No.:102,785

[52] US. Cl. 250/71 R, 250/106 R [51] Int. Cl. G01 n 23/00 [58] FieldofSearch ..250/71 R, 106 R, 77,84, 250/71.5 R

[56] References Cited UNITED STATES PATENTS 2,953,684 9/1960MacI-Iutchin et a1. 250/71 R 3,470,490 9/1969 Held et a1. 331/9453,026,436 3/1962 Hughes 250/106 R 3,260,846 7/1966 Feuer 250/106 R3,478,209 11/1969 Feuer 250/106 R 3,037,067 5/1962 Bartolomeim. 250/106R 2,956,162 10/1960 Armistead 250/7l.5 R

Primary Examiner-David Schonberg Assistant Examiner-Ronald .1. StemAttorney, Agent, or Firm-Wallenstein, Spangenberg, Hattis & Strampel 57ABSTRACT to enable the beta-electrons emitted by it to make directcontact with the phosphor. By embedding a fluorescent agent in thematerial of which the translucent body is formed, or by encapsulatingthe body in a material containing a fluorescent agent, the device may beutilized to transmit visible light.

11 Claims, 14 Drawing Figures PATENTED A 2 P INVENTOR SAMPSON Issues/asBETA ACTIVATED ULTRAVIOLET RADIATION SOURCE SURROUNDED BY A.VISIBLELIGHT PRODUCING FLUORESCENT AGENT The ability of radioactive materialsto excite phosphors to cause them to emit visible light has long beenrecognized and has led to the development of numerous devices whichutilizes this phenomenon. So far as is known, the primary, and only,purpose of these prior devices is to emit light in the visible range ofthe spectrum.

In accordance with one aspect of the present invention, highly useful,longlasting andsafe devices are provided which utilize radioactivesubstances and phosphors to emit radiation in the ultraviolet range ofthe spectrum. Thus, by way of illustration, the devices of thisinvention can be used in the form of self-energizing units to emitradiations in one band of the ultraviolet range of the spectrum to causetanning of the skin, or, in another form, as self-energizing germicidaland deodorizing units or, in still another form, as combinedself-energizing skin tanning, and germicidal and deodorizing units, forhome, laboratory or industrial use. In accordance with a further aspectof this invention, there are provided devices which utilize radioactivesubstances and phosphors capable of emitting radiation only in theultraviolet range of the spectrum for the excitation of fluorescentagents to produce light in the visible range of the spectrum. Whetherused for ultraviolet radiation or visible light radiation, the devicesof this invention enable the efficient use of the radioactive substancesand phosphors employed to provide selfenergizing units of the typementioned at low cost utilizing readily available and safe materials.

Briefly, the devices of this invention, in one form, comprise a hollow,translucent body portion fabricated of an ultraviolet radiationtransmitting material, the inner walls of which define a chamber. Thewalls of the chamber are provided with a thin coating of an ultravioletradiation emitting phosphor which is in contact with a low energybeta-electron emitting isotope or substance contained in the chamber. Byproper selection of the low beta-electron emitting substance andphosphor, a device can be constructed which is, as indicated, capable oftransmitting ultraviolet radiation having a wavelength suitable forsuntanning, or germicidal or deodorizing effects, or both. In anotherform, the devices of this invention can comprise a body portion asbefore, the material of which the body portion is fabricated, however,having particles, for example, of a fluorescent agent dispersed therein.The fluorescent agent in this form of the invention is characterized inthat it is capable of excitation by ultraviolet radiations to emit lightin the visible band of the spectrum. In a variation of this form of theinvention, the body portion is fabricated of an ultraviolet radiationtransmitting material which is encapsulated in, or coated with, afluorescent agent containing material which is capable of transmittingvisible light. The devices of this invention can embody reflectivesurfaces to direct and concentrate the radiations transmitted by them.In addition, they can be formed into any shape desired, and can be madeto emit visible light of any desired color or color combination.

The radioactive isotopes or substances having utility in the presentinvention are low energy beta-electron emitters, that is, they emitbeta-electrons having a particle energy of less than one MEV, especiallydesirably, particle energies of the order of about 0.01 to about 0.2MEV. Apart from their capability for emitting low energy beta-electrons,the radioactive substances should have a reasonably long half-life,preferably measured in years. The radioactive substances may ge gaseous,liquid or solid in nature, and should, of course, be availablecommercially and capable of being handled without the need for takingelaborate precautions to insure the safety of manufacturing personnel orthe ultimate user. Exemplary of radioactive substances which are usefulfor the purposes of the present invention are tritium, carbon-l4,nickel-63, sulfur-35, promethium- 147, and the like. Of this group,tritium is especially preferred. The maximum particle energy of theelectrons emitted by tritium is about 0.018 MEV, and tritium has a halflife of about 12.5 years. Because it is a gas, tritium lends itself toprocessing through a closed system thereby minimizing direct contact ofthe radioactive substance with personnel during fabrication of thedevices of this invention. Tritium has the further advantage of enablinggas pressure to be the determinating factor as to the quantity ofradioactive substance used in the devices of the present invention, thusfacilitating quality control and the production of devices which areuniformly safe for their intended use. In this connection, in thepreparation of devices in accordance with the teachings of thisinvention, excellent results are attained with tritium gas pressures ofless than one atmosphere, with pressures of the order of about 0.2 toabout 0.8, especially desirably about 0.5, atmosphere being preferred.Over and above the foregoing advantages, the use of tritium facilitatesthe fabrication of devices in accordance with this invention whichenables maximum utilization of the low energy betaelectrons emitted bythe tritium.

The phosphors useful in the fabrication of the devices of the presentinvention can be selected from a wide group, including both inorganicand organic phosphors. Typical of such phosphors are the inorganiccrystalline phosphors comprising the silicates, borates, phosphates,oxides, carbonates, iodides, tungstates, vanadates, tellurides, andsulfides of beryllium, calcium,

- magnesium, barium, strontium, manganese, zinc, cadmium and aluminum,or the like. It is customary to activate the phosphors with controlled,minute quantities of various metals. Exemplary of organic phosphorswhich can be used are anthracene, pentacene, quinine salicylate, phenol,atropine, rhodamine, benzidine, triphenylmethane, phloroglucinol, salol,and the like.

As indicated above, by proper selection of the radioactive substance andthe phosphor, devices can be fabricated in accordance with the presentinvention which are capable of emitting radiations in any desired bandof the ultraviolet spectrum. However, while devices can be made to emitradiations having a wavelength of the order of 500 A, generallyspeaking, devices capable of emitting radiations in the 2,000 A to 3,900N region vide radiation in the 3,l30 A band of the ultraviolet spectrumby using tritium as the radioactive substance and zinc sulfide activatedwith cerium and europium as the phosphor. Radiations in this range arecapable of tanning the human skin and the device, thus, can serve as anefficient, longlasting suntanning unit. Both types of phosphors can, ofcourse, be combined in the same device to provide a unit capable ofperforming each of the aforementioned functions. Still further, by wayof illustration, a device capable of emitting radiations in the 3,650 Aregion of the ultraviolet spectrum can be prepared with tritium as theradioactive substance and calcium phosphate activated with cerium andgadolinium as the phosphor. Ultraviolet radiations of this order ofmagnitude can excite many fluorescent agents to produce light in thevisible range of the spectrum. Thus, by utilizing a radioactivesubstance which emits beta-electrons having extremely low particleenergy levels in conjunction with a phosphor which is excited by suchlow energy particles to produce ultraviolet radiations, a safe,longlasting device can be produced in accordance with the teachings ofthe present invention which can emit light of any desired color or colorcombinations in the visible light range of the spectrum. Typical offluorescent agents which are useful for this purpose are acetylsalicylicacid, alizarin, aminophyllin, aniline, atropine sulfate, bariumsuccinate, butyrone, cadmium sulfide, calcium mandelate, chlorophyll,chromium stearate, cobaltous resinate, emetine, fluorescein, galliumgluconate, hydrastin, hyoscyamin, lead naphthenate, lithium salicylate,magnesium 6- hydroxyquinoline, manganese resinate, mesobilirubin, methylhexaline, musk xylol, B-naphthol, naphthalene, nicotine, orcin,phenanthrene, podophyllin, potassium salicylate, proto-porphyrin,resorcinol, rhodacene, riboflavin, samarium gluconate, sodiumbarbiturate, strontium stearate, theobromine, -tin stearate, uracil,vanadyl cyanide, zinc palmitate, zinc 8- hydroxyquinoline, zinc sulfide,zinc valerate, calcium tungstate, and the like, and compatible mixturesthereof.

The devices of the invention, both as to their construction and methodof operation, together with additional objects and advantages thereof,will be more fully understood from the following description ofillustrative specific embodiments when read in conjunction with theaccompanying drawing in which:

FIG. I is an enlarged vertical sectional view of an embodiment of oneform of a device of this invention;

FIG. 2 is a sectional view taken substantially along line 22 of FIG. 1;

FIG. 3 is an end view of another embodiment ofa device of this inventionwhich embodies the form of the invention shown in FIG. 1;

FIG. 4 is an enlarged vertical sectional view of an embodiment of yetanother form of a device of the present invention;

FIG. 5 is a sectional view taken substantially along line 55 of FIG. 4;

FIG. 6 is a fragmentary sectional view taken substantially along line 66of FIG. 4;

FIG. 7 is an enlarged vertical sectional view of an embodiment of yetanother form of a device of this invention;

FIG. 8 is a sectional view taken substantially along line 8-8 of FIG. 7;

FIGS. 9 and I0 are vertical sectional views of embodiments of otherforms of devices of the present invention;

FIG. II is a fragmentary top plan view of an embodiment of still anotherform of a device of this invention;

FIG. 12 is a vertical sectional view taken substantially along line l2l2of FIG. 11; and

FIGS. 13 and 14 are side views in elevation, partly in section, ofshaped articles comprising embodiments of the devices of the presentinvention.

Referring, now, in greater detail to FIGS. 1 and 2 of the drawing, theembodiment of the invention shown comprises a hollow, elongated, tubularbody portion 10 which is sealed at both ends. The body portion 10 may befabricated of any suitable ultraviolet radiation transmitting materialsuch as glass or a plastics material which is impermeable and chemicallyresistant to the radioactive substances and phosphors having utility forthe purposes of this invention. The inner wall of the body portion 10defines a chamber 12 adapted to hold a radioactive isotope or substancewhich may be in a solid, liquid or gaseous state. In the embodiments ofthe devices illustrated, gaseous tritium is employed as the radioactivesubstance. The inner wall of the body portion 10 has a coating, filmorlayer 14 of a phosphor, or combination of phosphors, thereon. Asindicated, the phosphors employed in the devices are characterized inthat they are capable of excitation by low energy beta-electrons toproduce ultraviolet radiation. The phosphors advantageously are utilizedin a crystalline or particulate form and may be adhered or bonded to theinner wall of the body portion in any manner known in the art. Thus, byway of illustration, the particles of the phosphor can be bonded to thesurface of the inner walls of the body portion 10 with inorganicadhesives such as sodium silicate or potassium silicate. The averageparticle sizeof the phosphor employed is somewhat variable. However, thegenerally optimum objectives of the invention are retained with phosphorparticle sizes ranging from about 1 to about 2 00, especially desirablyabout 2 to about 100, microns. The depth of the phosphor coating, filmor layer 14, also, is variable, and will depend in large measure uponthe energy level of the beta-electrons emitted by the radioactivesubstance in the chamber. 12. Generally speaking, however, utilizing lowenergy beta-electron emitting radioactive substances of the typedescribed hereinabove, excellent results can be achieved with phosphordepths of the order of about 1 to about 20, usually about 3 to about 15,microns.

Since the trajectory range of the beta-electrons emitted by tritium isof the order of about 2.5 to about 3 millimeters, the dimensions of thechamber 12 should be such that the beta-electrons emitted by the tritiumin the chamber 12 will be substantially completely absorbed by thephosphor coating, film or layer 14, and will not penetrate the walls ofthe body portion 10. Further, in this same connection, by employing achamber having a small cross-sectional area, the quantity of tritiumintroduced into the chamber can be regulated to maximize utilization ofthe energy of the beta-electrons emitted by the tritium. Stateddifferently, the devices of the present invention enable the use of lowenergy beta-electron emitting isotopes or substances in concentrationssuch that any loss of energy of the electrons due, for example, toquenching, or collision between the electrons, is minimized and, as aconsequence, a greater number of the electrons make contact with thephosphor, or phosphors, on the surface of the chamber. This moreefficient use of the emissions of the radioactive substance not onlyenables the production of devices which a re safe to use, but, also, hassignificant cost advantages. As indicated earlier hereinabove, thepressure of the tritium in the chamber 12 will be less than atmosphericpressure to provide greatest security against leakage from the sealedends of the body portion 10. A wide variation of energy levels oftritium can be introduced into the chamber 12 while maintaining internalpressures of one atmosphere or less.

As shown in FIG. 3, a unit for providing a substantial amount ofultraviolet radiation, and for concentrating the radiation upon adesired object or surface, can be made by forming a bundle I8 comprisedof a plurality of devices corresponding to those shown in FIGS. 1 and 2.The bundle 18 may be formed byadhering or fusing the outer walls of thedevices together or by wrapping or binding them together with a suitablematerial. In this latter connection, the wrapping or binding materialmay be a radiation insulating matrix thereby enabling the ultravioletradiations produced by the multiplicity of wrapped or bound devices tobe projected only from either one, or both, ends of the bundle. Thebundle, of course, may be of any desired shape, size and crosssectionalarea.

Referring, now, to FIGS. 4, 5 and 6 of the drawing, the embodiment ofthe device illustrated and designated generally by reference numeral 20incorporates an inner, ultraviolet radiation emitting unit 22 which,like the device shown in FIGS. l and 2, comprises a hollow, elongated,tubular body portion 24, the ends of which have been sealed. The innerwalls of the body portion 24 define a chamber 26 .which contains a lowenergy beta-electron emitting radioactive substance such as tritium. Thesurface of the inner walls of the body portion 24, as in the device ofFIGS. 1 and 2, is provided with a thin coating, film or layer 28 of aphosphor, or mixture of phosphors, capable of excitation by the lowenergy beta-electrons emitted by the radioactive substance in thechamber 26 to produce ultraviolet radiations. The device 22 issurrounded by, or encapsulated in, an outer wall portion or shell 30formed of a light transmitting material such as glass, quartz, mica orclear plastics material. Embedded in the shell 30, and substantiallyuniformly dispersed therein, are particles 32 of a fluorescent agent,the particles being characterized in that they are capable of excitationby ultraviolet radiations in the 3,650 A band of the spectrum to producevisible light. Particles of different fluorescent agents can, of course,be employed to produce light of more than one color. The wall portion orshell 30 may be of substantially uniform thickness, or, as shown in FIG.5, it may be made thicker along one side to impart a lens effect to thedevice 20.

The embodiment of the device of this invention, shown in FIGS. 7 and 8,incorporates an inner, ultraviolet radiation transmitting portion which,like the previously described embodiments of the invention, comprises ahollow, elongated tubular body portion 42 which is sealed at its ends.The inner walls of the body portion 42 define a chamber 43 for holding aradioactive substance of the type referred to hereinabove. The surfacesof the inner walls of the body portion 42 are provided with a coating,film or layer 44 of a phosphor,

or phosphors, capable of being excited to produce ultraviolet radiationsin the 3650 A band of the spectrum. The ultraviolet radiationtransmitting portion 40 is encased or encapsulated in a lighttransmitting shell or housing 46. The shell or housing 46 has agenerally convex, light transmitting front wall 48, and a substantiallyplanar, ultraviolet radiation reflecting rear wall 50'. The front wall48 has embedded in it particles 52 of a fluorescent agent capable ofconverting ultraviolet radiation into visible light. Mixtures offluorescent agents, of course, can be employed to provide differentcolor effects. The rear wall 50 is coated on its inner-surface with amaterial, such as aluminum, silver, cadmium or titanium dioxide, capableof reflecting transverse rays of ultraviolet radiation back into thefront wall 48. 1

The embodiment of the invention illustrated in FIG. 9 of the drawingcomprises a hollow, disc-shaped, ultraviolet radiation transmitting body60, the .inner walls of which define a chamber 62 for holding aradioactive substance such as tritium. A hollow, tubular extension 64 isjoined to the body substantially centrally of the inner wall 66 thereof,and is sealed off from the chamber 62. The extension 64 can be used toanchor the device in a support member (not shown). The inner surface ofthe generally flat outer wall 68 of the body 60 is provided with acoating, film or layer 70 of a phosphor, of mixture of phosphors, which,upon excitation by low energy beta-electrons emitted by the radioactivesubstance in the chamber 62, is capable of transmitting ultravioletradiations in the 3,650 A band of the spectrum. Joined to the body 60 atthe .outer wall 68 thereof, is a light transmitting, generally convexcover portion 72 in which are embedded particles 74 of a fluorescentagent, or a mixture of such agents, which are capable of excitation bythe ultraviolet radiation emitted by the body 60 to produce light in thevisible range of the spectrum. A disc-shaped housing 76 is provided toreceive the body 60 and the extension 64. The housing 76 advantageouslyis fabricated of an ultraviolet radiation reflecting material such asaluminum, or the surfaces thereof which are in contact with the body 60are provided with a coating of an ultraviolet radiation reflectingmaterial such as aluminum, cadmium, silver, titanium dioxide, or thelike. i

In FIG. I0, the embodiment of the invention illustrated comprises adisc-shaped, ultraviolet radiation transmitting body 80, the walls ofwhich define a chamber 82 for holding a radioactive substance such astritium. The outer wall 84 of the device has a generally convexconfiguration, and is provided on its inner sur face with a coating 86of a phosphor, or mixture of phosphors, capable, upon excitation by thelow energy beta-electrons emitted by the radioactive substance in thechamber 82, of producing ultraviolet radiations in the 3,650 A band ofthe spectrum. The outer wall 84, further, has embedded in it particles88 of a fluorescent agent, or a mixture of such agents, which willrespond to the ultraviolet radiations to produce visible light. Joinedto the body 80, centrally of the inner wall 90 thereof, is a tubularsupport extension 92. A housing 94, having an inner surface capable ofreflecting ultraviolet radiation, is provided for the body 80.

The embodiment of the invention illustrated in FIGS. 11 and 12, like thetwo previously described embodiments, comprises a generally disc-shapedultraviolet radiation transmitting body 100, having a chamber 102 forholding a radioactive substance. The inner surfaces of the outer, flatwall 104, and the side wall 106, are coated with a thin film or layer108 of a phosphor, or mixture of phosphors, of the type used in the twopreviously described embodiments. The outer wall 104, and the side wall106, in addition, have embedded in them particles 1 of a fluorescentagent, or agents, capable of emitting light in the visible range of thespectrum in response to ultraviolet radiation. A tubular supportextension 112 is joined to the body 100. The inner wall 114 of the body100 is in contact with an ultraviolet radiation reflecting surface 116.The body 100 is completely ringed by, and supported in, a plasticsmaterial 118 capable of transmitting light radiations emitted by thebody 100. The plastics material 118 advantageously is of a colordifferent from the color of the light waves emanating from the walls 104and 106 of the body 100 thereby to give a multicolor effect.

In the embodiments shown in FIGS. 9 through 12, the chamber for holdingthe radioactive isotope or substance can, in each instance, be used as areceiving chamber for a device as illustrated in FIG. 1. Coating of theinner surfaces of the receiving chamber walls with a phosphor, asdescribed, is optional in this case, and will depend upon the lighttransmitting effects sought to be attained with the devices.

In FIGS. 13 and 14, there are shown constructions which illustrate theversatility of the devices of the present invention. The constructionshown in FIG. 13 comprises a continuous, convoluted, elongated, hol low,tubular ultraviolet radiation body 120 encased, or encapsulated, in alight transmitting panel 122 fabricated, for instance, of a clear glassor plastics material. The body 120 is sealed at both ends, and the wallsthereof define a chamber 124 for holding a radioactive substance. Theinner surface of the walls of the body 120 has a coating, film or layer126 of a phosphor, or mixture of phosphors, capable of emittingultraviolet radiation in the 3,650 A range of the spectrum. The panel122 has particles 128 of a fluorescent agent, or a mixture of suchagents, embedded therein, the particles, as before, responding toultraviolet radiation of the wavelength indicated to produce visiblelight.

The construction shown in F1G.'14 comprises a hollow, tubularultraviolet radiation body 130 in the shape of the number 3. As in thepreviously described construction, the ends of the body 130 are sealed,and the walls thereof define a chamber 132 for holding a radioactivesubstance such as tritium. The inner surface of the walls of the body130 are provided with a thin coating, film or layer 134 of a phosphor,or mixture of phosphors. The body 130 is encased, or encapsulated, in aclear light transmitting material 136 having embedded therein particles138 of a fluorescent agent, or mixture of fluorescent agents, capable ofproducing visible light in response to the ultraviolet radiationstransmitted by the body 130. The fluorescent agents used desirablyprovide visible light of different colors, and are dispersed in thematerial 136 in a manner such that separate zones, each radiating lightof a different color, are visible in theconstruction.

As stated previously hereinabove, the low energy beta-electron emittingisotope or substance may be in a solid, liquid or gaseous state. Thus,by way of specific illustration, the low energy beta-electron emittingsubstance may comprise solid particles of promethium-l 47 dispersed orsuspended in a clear, inert liquid medium such as mineral oil orglycerin. The quantity of the solid isotope employed in the liquid.medium is variable. However, from the standpoint of safety and economicconsiderations, the quantities used will range from about 0.1 to about-lor 2 percent, by weight, of the dispersion or suspension. The size ofthe particles used ad vantageously will range from about 1 to about 100mi crons.

It will be apparent from the foregoing description that the devices,apart from their utility as a source of ultraviolet radiation to bringabout tanning of the human skin, or to provide deodorizing or germicidaleffects, also have important uses in other areas. Thus, for example, thedevices can be used as signals or warning lights on motor vehicles,trailers, boats, and bicycles. In addition, they can be used as vehicledashboard or clock dial lights, or as a source of ultraviolet radiationfor illuminating dials, telephone buttons, panels, or the likecontaining luminous materials. More specifically in this latterconnection, by selecting a phosphor which emits radiation in the 3,650 Aregion, and by utilizing a nickel-cobalt glass tube that screens outradiations in the visible part of the spectrum but allows the passage ofultraviolet radiations in the 3,650 A region, a compact, self-containedand self-energized source of 3,650 A radiation is obtained which can beused, for example, to illuminate fluorescent treated watch and clockdials, to inspect foods, in laboratory studies, and

the like. Other uses and modifications of the devices will, of course,suggest themselves to those skilled in the art in the light of theforegoing description. It should be understood, therefore, that thepresent invention includes all such modifications which fall within thescope of the appended claims.

What is claimed is:

1. A device having utility as an ultraviolet radiation generated lightsource comprising a hollow, translucent body portion formed of anultraviolet radiation transmitting material having dispersed thereinparticles of a fluorescent agent capable of excitation by ultravioletradiations to produce visible light, the inner walls of said bodyportion defining a chamber, a thin coating of an ultraviolet radiationemittingphosphor on the walls of the chamber, said phosphor beingcapable of excitation by low energy beta-electrons having a particleenergy of about 0.01 to about 0.2 MEV to produce only ultravioletradiation having a wavelength sufficient to cause the fluorescent agentparticles to produce visible light, and-a low energy beta-electronemitting substance in said chamber, said substance being capable ofemitting beta-electrons having a particlefenergy of about 0.01 to about0.2 MEV.

2. A device as claimed in claim 1 wherein the betaelectron emittingsubstance is tritium.

3. A device as claimed in claim 1 wherein a phosphor, or a mixture ofphosphors, is used which is capable of emitting ultraviolet radiationhaving a wavelength of about 3,650 angstroms.

4. A device as claimed in claim 1 wherein the hollow, translucent bodyportion comprises a small diameter cylinder, the ends of which aresealed.

5. A device as claimed in claim 3 wherein the phosphor is calciumphosphate activated with cerium and gadolinium.

6. A device as claimed in claim 3 wherein the phosphor is zinc sulfideactivated with cerium and europlum.

7. A device as claimed in claim l wherein the betaelectron emittingsubstance is in the form of solid particles dispersed in an inertliquid.

8. A device as claimed in claim 1 wherein the betaelectron emittingsubstanceis sealed from the group consisting of tritium, promethium-l47,sulfur-35, nickel-63 and carbon-l4.

9. A device for transmitting light in the visible range of the spectrumcomprising a hollow, translucent body portion formed of an ultravioletradiation transmitting material, the inner walls of which define achamber and the outer surface of which has a layer of a fluorescentagent capable of excitation by ultraviolet radiations to produce visiblelight, a thin coating of an ultraviolet radiation emitting phosphor onthe inner walls of the chamber, said phosphor being capable ofexcitation by low energy beta-electrons having a particle energy ofabout 0.01 to about 0.2 MEV to produce only ultraviolet radiation havinga wavelength sufficient to cause the fluorescent agent on the outersurface of the body portion to produce visible light, and a low energybetaelectron emitting substance in the chamber of the body portion, saidsubstance being capable of emitting betaelectrons having a particleenergy of about 0.01 to about 0.2 MEV. v

10. A device as claimed in claim 9 wherein the low energy beta-electronemitting substance is tritium.

11. A device as claimed in claim 9 wherein the body portion is formed ofa material capable of transmitting ultraviolet radiations in the 3,000 Nto 3,900 A region of the spectrum and screens out radiations in thevisible region of the spectrum.

2. A device as claimed in claim 1 wherein the beta-electron emittingsubstance is tritium.
 3. A device as claimed in claim 1 wherein aphosphor, or a mixture of phosphors, is used which is capable ofemitting ultraviolet radiation having a wavelength of about 3,650angstroms.
 4. A device as claimed in claim 1 wherein the hollow,translucent body portion comprises a small diameter cylinder, the endsof which are sealed.
 5. A device as claimed in claim 3 wherein thephosphor is calcium phosphate activated with cerium and gadolinium.
 6. Adevice as claimed in claim 3 wherein the phosphor is zinc sulfideactivated with cerium and europium.
 7. A device as claimed in claim 1wherein the beta-electron emitting substance is in the form of solidparticles dispersed in an inert liquid.
 8. A device as claimed in claim1 wherein the beta-electron emitting substance is sealed from the groupconsisting of tritium, promethium-147, sulfur-35, nickel-63 andcarbon-14.
 9. A device for transmitting light in the visible range ofthe spectrum comprising a hollow, translucent body portion formed of anultraviolet radiation transmitting material, the inner walls of whichdefine a chamber and the outer surface of which has a layer of afluorescent agent capable of excitation by ultraviolet radiations toproduce visible light, a thin coating of an ultraviolet radiationemitting phosphor on the inner walls of the chamber, said phosphor beingcapable of excitation by low energy beta-electrons having a particleenergy of about 0.01 to about 0.2 MEV to produce only ultravioletradiation having a wavelength sufficient to cause the fluorescent agenton the outer surface of the body portion to produce visible light, and alow energy beta-electron emitting substance in the chamber of the bodyportion, said substance being capable of emitting beta-electrons havinga particle energy of about 0.01 to about 0.2 MEV.
 10. A device asclaimed in claim 9 wherein the low energy beta-electron emittingsubstance is tritium.
 11. A device as claimed in claim 9 wherein thebody portion is formed of a material capable of transmitting ultravioletradiations in the 3,000 A* to 3,900 A* region of the spectrum andscreens out radiations in the visible region of the spectrum.